These studies are aimed at extending our observations on the properties of the intestinal cell surface in health and disease. Emphasis will be directed at the transport of sugars and amino acids by vesicles of isolated microvillus and lateral-basal membranes of the intestinal cell. These studies will include the kinetics, driving forces and mechanism of glucose, amino acid and electrolyte transport as well as the interactions between these nutrients. Studies will be carried out with reconstituted vesicles (liposomes). Binding studies and specific labeling of the intestinal sodium-dependent glucose-carrier are planned in order to better define the defect responsible for glucose-galactose malabsorption in man. We plan to perfect a method (using free-flow electrophoresis) so that membrane studies can be carried out on intestinal biopsy specimens. We hope to investigate membrane function in experimental and clinical disorders such as diabetes, bacterial toxin-induced diarrhea and genetic diseases such as cystinuria and Hartnup disease.